1. Field of the Invention
The present invention relates to a fluid pressure regulator for regulating the pressure or flow rate of a fluid.
2. Description of the Related Art
Heretofore, controlling the pressure or flow rate of a fluid with a fluid pressure regulator has widely been known.
For example, Japanese Patent Publication No. 7-50418 discloses a pneumatic pressure regulator which operates as follows: For regulating the pressure of a fluid discharged from a main valve, the pressure of the discharged fluid is detected by a pressure sensor, and a detected signal from the pressure sensor is compared with a preset value by a controller. The controller outputs a pulse signal depending on the comparison result to a two-port solenoid-operated valve for supplying the fluid or a two-port solenoid-operated valve for discharging the fluid. The pneumatic pressure regulator increases or reduces a pilot pressure depending on pneumatic pressure pulses supplied from either one of the solenoid-operated valves to open or close a fluid supply valve body coupled to a diaphragm chamber (pilot chamber) for thereby regulating the pressure of the fluid discharged from a main valve to a preset pressure.
FIG. 5 of the accompanying drawings shows a conventional fluid pressure regulator 1 having a drive controller 5 which is supplied with a desired preset value or a desired control program through an external controller 2. The drive controller 5 compares the desired preset value or the desired control program with a detected signal from a sensor 10. The drive controller 5 then outputs a drive signal, which has been PID-converted (proportional plus integral plus derivative) based on the comparison result, to a solenoid-operated valve 6 for supplying the fluid and/or a solenoid-operated valve 7 for discharging the fluid. In response to the drive signal, the solenoid-operated valve 6 and/or solenoid-operated valve 7 is opened or closed to control the supply of the fluid or the discharge of the fluid by a pilot valve 8. The pilot valve 8 then operates a fluid supply valve and/or a fluid discharge valve of a main valve 9 for thereby regulating the pressure or flow rate of the fluid supplied from a fluid pressure source (not shown) to a controlled object 4.
As shown in FIG. 6 of the accompanying drawings, the external controller 2 stores different control programs as patterns P1, P2, P3 for controlling the fluid pressure with respect to time. The external controller 2 outputs a command for selectively executing the stored control programs. The external controller 2 comprises a general sequencer or personal computer. The external controller 2 has various functions including control, decision, processing, arithmetic, and storage functions.
The controlled object 4 may be a device for controlling an internal pressure or a fluid quantity in a fluid tank, or a device for controlling a vacuum within a vacuum chamber of a semiconductor control apparatus.
A detecting mechanism 3, which may be added when necessary, comprises some of various sensors and measuring units selected depending on the accuracy of a control range for a controlled variable required by the controlled object 4.
The external controller 2 and the detecting mechanism 3 are installed by the user.
In order to input the preset value or the control program to the controller of the pneumatic pressure regulator disclosed in the Japanese Patent Publication No. 7-50418 or the drive controller 5 of the fluid pressure regulator 1 shown in FIG. 5, it is necessary for the user to select a general sequencer or personal computer for use as the external controller 2 and install the selected sequencer or personal computer with a program having various desired functions. Therefore, the resultant system is highly expensive.
It is a general object of the present invention to provide a fluid pressure regulator which is low in cost and which is a space saver.
According to the present invention, a fluid pressure regulator is low in cost and is a space saver because there is no need to install an external controller for the fluid pressure regulator.
The fluid pressure regulator has a PID controller for comparing, processing, and calculating a control signal inputted from a second PID controller based on a detected signal from a sensor, and converting the resultant signal into a PID signal. The PID controller can thus output a highly accurate control signal to a drive controller for actuating solenoid-operated valves.
A controlled variable in a controlled object which is associated with the fluid pressure regulator is detected and supplied to the second PID controller through a feedback loop. Consequently, the controlled variable in the controlled object can be adjusted with high accuracy.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.